Such insulation hangers are widely used in furnaces or other similar installations and usually comprise a stud weldable metal stud or ceramic stud and an associated quarter-turn washer. The stud may be made of relatively high temperature resistant material such as stainless steel or other sophisticated alloys and is normally stud welded to the furnace or other type wall. Batt type insulation material is then impaled upon the stud and held in place by a quarter-turn washer to secure the insulation materials to the wall of the furnace or other structure. Examples of prior art insulation hangers utilizing such studs and quarter-turn washers may be seen, for example, in Nelson U.S. Pat. No. 2,412,744, Rutter et al U.S. Pat. No. 3,523,395, Walker U.S. Pat. No. 3,738,217 and McLean U.S. Pat. No. D-265,288. The latter patent is a design patent on the configuration of the stud used in the widely employed ULTRA-LOK insulation hanger manufactured and sold by the Erico Jones Company of Dayton, Ohio.
As noted, the insulation hangers of the above prior art employ a bayonet-type or quarter-turn washer which is inserted over the stud and then rotated 90.degree. to lock behind a formed projection or cut notch on the stud to contain the insulation material between the washer and the wall to which the stud is secured. Similar studs may be secured by adhesive as shown, for example, in Eckel U.S. Pat. No. 2,697,857.
In prior devices such as shown in the Walker, Rutter et al and the ULTRA-LOK design, insulation applications in situations where vibration may occur such as through the employment of blowers, burners, or conveyors, or normal shipboard vibrations, may tend to cause the quarter-turn washer to rotate from its locking position. This problem is particularly aggravated if the insulation materials tend to shrink throughout their service life. The problem is also aggravated if the stud extends in a slightly downwardly direction or vertically as when the insulation hanger is employed to secure insulation materials to the underside of a wall or ceiling of a furnace. In some few instances, the quarter-turn washer has been known to become loose and in some further instances, has been known to fall off of the stud thus in effect releasing the insulating material.
When forming insulation hangers, it is preferred to utilize round stock. Such round stock initially does not require a subsequent flattening or slitting operation to form flattened stock, and moreover if notches are to be cut therefrom as in the above mentioned Walker patent, the cross-sectional area of the stud is not reduced nor are scrap losses generated, nor are notch sensitive or stress riser areas formed on the elongated stud. This is important in the manufacturing operation from metal stock since notching requires expensive dies which must be continually replaced and/or sharpened. Moreover, the material from which the stock is made has to be temperature sensitive and the alloys involved such as stainless steel or INCONEL are quite expensive. Moreover, the service life of any insulation hanger, if formed of metal, is directly proportional to its cross-sectional area at the hot face. Obviously, notching or stock removal reduces that cross-sectional area and thus reduces the service life of the hanger. Further, in stud welding round stock as opposed to flattened stock, considerably less energy is required to form a sound weld between the stud and the wall to which it is affixed. In this manner a stud formed from round stock provides a more efficient insulation hanger and also provides an insulation hanger with a longer service life if the cross-sectional area thereof is not diminished significantly in its formation. It has, for example, been calculated that a flattened stud such as utilized in the aforenoted ULTRA-LOK hanger assembly has approximately 75% more cross-sectional area at the hot face than does a flatttened and notched stud as shown in the aforenoted Walker Pat. No. 3,738,217.
However, as noted in connection with all of the prior art studs, vibration in a furnace or other insulating environment may tend to cause the washer to rotate from its locking position.